I bought my 06 X5 4.4 from BMW dealership and they did the valve stem seals before I purchased. It has 149000 miles on it and I have a 18,000 mile extended warranty through dealership. I asked them to check timing chain guide rails while they were in there and said they were in good condition. Have the valve stem seals design/integrity been updated so this won't happen again? How do I prevent this from happening again? What preventive maintenance and type of oil going forward? I love this ride and want to keep it well over 250k it possible. It's in immaculate condition. I'm changing transfer case fluid with BMW oem and differentials with Amsoil 75w-90 Severe gear this weekend. I am also changing the two pressure regulator valves as well. I even lubed the panoramic sunroof tracks.

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2006 X5 4.4i | Build Date: 12/2005
Sterling Grey on Schwarz
Sport | Premium | Cold Weather
OEM V Spoke Wheels